SCAT Classification of Gaia22bil (AT2022gpp) as a Likely Optical Changing-Look AGN
ATel #15329; J. T. Hinkle, B. J. Shappee, C. Ashall, D. Desai, T. de Jaeger, A. Do, M. E. Huber, A. V. Payne, M. A. Tucker (IfA, Hawai'i)
on 14 Apr 2022; 01:04 UT
Credential Certification: Jason Hinkle (jhinkle6@hawaii.edu)
Subjects: Optical, AGN, Black Hole, Transient
Gaia22bil (AT2022gpp) was discovered by the Gaia satellite (Gaia Collaboration et al. 2016) on UT 2022-03-27.40 at G = 18.56 mag. The source began to brighten significantly in August 2021 and relative to the archival Gaia photometry is currently ~0.8 mag brighter. An archival Sloan Digital Sky Survey (SDSS; York et al. 2000) spectrum of the host galaxy WISEA J151320.88+175915.9 indicates that the source redshift is z = 0.12974 and the galaxy hosted Seyfert 2 AGN.
A classification spectrum was obtained with the Supernova Integral Field Spectrograph (SNIFS; Lantz et al. 2004) on the University of Hawaii 88-inch telescope on 2022-04-11 as part of the Spectral Classification of Astronomical Transients (SCAT) program (ATel #11444). The spectrum shows a roughly flat continuum with a broad (~5500 km/s) H-alpha emission line at the host galaxy redshift, consistent with the spectrum of a Seyfert 1. The H-alpha line also appears to have a strong red wing at a velocity of ~3000 km/s from the nominal H-alpha line center.
In addition to the Gaia Alerts photometry, we also obtained archival light curves of WISEA J151320.88+175915.9 from the Catalina Real-time Transient Survey (CRTS; Drake et al. 2009), All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014, Kochanek et al. 2017), and Asteroid Terrestrial-impact Last Alert System (ATLAS; Tonry et al. 2018) to search for previous activity. Besides the flare associated with the transient Gaia22bil, there is no large-amplitude variability observed, consistent with the archival Seyfert 2 classification. The standard deviation reported by Gaia for their archival data is 0.16 mag, well below the amplitude of the current flare. Based on the large flux increase and the appearance of broad emission lines, we classify Gaia22bil as a likely optical changing-look AGN in WISEA J151320.88+175915.9.
